A characteristic feature of many rheumatic diseases is the presence of circulating antinuclear antibodies. Assays based on the measurement of these antibodies are established in the clinical laboratory for the diagnosis of these diseases, but often without the benefit of having well characterized or isolated target antigens. One such autoimmune disease is scleroderma or progressive systemic sclerosis. The objective of this proposal is to provide sensitive and quantitative diagnostic/prognostic assays for this disease by developing assays based on the direct binding of serum antibodies to recombinant polypeptide antigens. The initial focus will be on the five polypeptides identified with the two major scleroderma-associated antigens, scl-70 and centromere. The antigens will be isolated in quantities sufficient for microsequencing. Oligonucleotide probes based on these sequences will be used to clone the genes coding for these polypeptides from human cDNA libraries. Expression of the cloned genes will allow for the synthesis of gram amounts of antigen sufficient for the development of the assay. The recombinant polypeptides will also be used as immunogens to insure a constant and abundant supply of antibodies for antigen isolation and ultimately assay standardization. Similar efforts will be directed toward other of the scleroderma-associated antigens, including fibrillarin, PM-Scl and Ku, to obtain an inclusive and representative panel of diagnostic probes to encompass the clinical variants of this disease.